New York, New York - Columbia University, the epicenter of pro-Palestinian protests that have upended college campuses across the US, began suspending student demonstrators on Monday after they defied an ultimatum to disperse.

Overnight, protesters occupied a campus building, barricading themselves inside while several others formed a human chain outside, according to videos posted on social media.

"Columbia community members took back Hamilton Hall just after midnight," student group Columbia University Apartheid Divest said in a statement.

A banner with the words "Hind's Hall" was unfurled, referencing six-year-old Hind Rajab, who was killed along with her family in an Israeli airstrike as she pleaded for help.

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Columbia began suspending students following almost two weeks of protests against Israel's war in Gaza that have swept through higher education institutions from coast to coast, after around 100 protesters were first arrested at Columbia on April 18.

In the latest crackdown, authorities demanded that the protest encampment be cleared by 2:00 PM or students would face disciplinary action.

"These repulsive scare tactics mean nothing compared to the deaths of over 34,000 Palestinians," said a statement, read out by a student at a press conference after the deadline, referring to the death toll caused by Israel in Gaza.

"We will not move until Columbia meets our demands or... are moved by force," said the student, who would not give his name.

The demonstrators – backed by faculty members who formed a human chain to protect them from police – have vowed to remain at the hall until their demands are met. Among them is that the institution divests financial holdings linked to Israel.

Columbia vice-president of communications Ben Chang said the university had "begun suspending students as part of this next phase of our efforts to ensure safety on our campus."

He said students had been warned they would be "placed on suspension, ineligible to complete the semester or graduate, and will be restricted from all academic, residential, and recreational spaces."

Columbia University president Minouche Shafik, in a statement Monday announcing talks had broken down, said: "Many of our Jewish students, and other students as well, have found the atmosphere intolerable in recent weeks."

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"Many have left campus, and that is a tragedy," she said, without specifying how many Jewish students had left.

"Anti-Semitic language and actions are unacceptable and calls for violence are simply abhorrent."

Protest organizers deny accusations of anti-Semitism, arguing their actions are aimed at Israel's government and its prosecution of the conflict in Gaza. They also insist non-student agitators have engineered some of the incidents.

One graduate student protester, who asked to be identified only as "Z," told AFP: "It's finals week, everyone is still working on their finals. But at the end of the day, school is temporary".

Police on Monday also violently cracked down on anti-war encampments at the University of Texas at Austin, Virginia Commonwealth University, while suspensions were underway at Cornell University.